Abstract methods (including methods in interface) should be commented by Javadoc. Examples:
<pre>
    /**
     * fetch data by rule id
     *
     * @param ruleId rule id
     * @param page page number
     * @param jsonContext json format context
     * @return Result<XxxxDO>
     */
    Result<XxxxDO> fetchDataByRuleId(Long ruleId, Integer page, String jsonContext);
</pre>